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Locating Groundwater Inflow Sites in Estuaries
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Project Title: Measurement System for Localizing Groundwater Flows
into an Estuarine Environment
Research Locations: Chesapeake Bay, MD
Last Update: 2-28-02
Groundwater inflow into estuaries and coastal areas is far more important than previously thought. Groundwater is capable of transporting contaminants into estuaries, and therefore the ability to detect, survey and localize groundwater inputs is essential for managing contaminant inputs to coastal waters. This project is developing technology to rapidly detect, map and localize groundwater inflow into rivers and estuaries to improve environmental monitoring and remediation assessment activities.
Design
The characteristics of groundwater differ from those of surrounding estuarine
water. Project researchers, therefore, set out to design software and
hardware that would enable users to quickly and efficiently detect and
record these differences. They designed a towed sensor system using a
custom sled and boom (see Figures 1 and 2). The sled housed a pressure
sensor, three temperature sensors at different depths and an inclinometer
to maintain a consistent boom angle. Water samples were collected from
the sled and pumped up to the boat where other sensors (e.g., pH, conductivity)
monitor the samples.
Results
- The technology was successful in detecting groundwater inflow sites in water as deep as 12 feet.
- Figure 3 shows results from a survey of an estuarine site in Delaware. Notice the clear groundwater signature, especially in temperature (top graph) and conductivity (middle graph). (The three lines for temperature represent readings from the three thermistors, each at a different depth. The shallowest thermistor did not record the inflow site). The conductivity and pH (bottom graph) results lag behind the temperature results because those sensors were located on the boat rather than on the sled.
A More Flexible System
The system currently requires calm water and survey paths that
are clear of obstacles. However, the system can be retooled to be
operable in more challenging conditions.
Expand the Sensor Array
New sensors can be added to the system depending on the specific application. As more sensors are added, it becomes easier to differentiate groundwater from the estuarine water. Scientists from the US Geological Survey are considering adding several new sensors to this system for applications in Delaware and Virginia.
How-To Information
A CD-ROM with complete instructions on how to build and use the system (which includes custom-designed software) is currently being developed.
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Project Coordinator
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Charles Sarabun John Hopkins Applied Physics Lab (240)228-5794 charles.sarabun@jhuapl.edu |
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Start-End Date:
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09/01/1999 -09/01/2001
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NERR Reserve(s):
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Chesapeake Bay, MD
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| For more information: |
Dolores Jalbert Leonard Phone: (603) 862-3685 Email: dolores.leonard@unh.edu |